The proposed research is to understand the biochemical expression of aging in the reproductive tissue at the cellular level. We have selected the avaian embryonic ovary as the model system. With this model system we are able to compare the changes in aging and growing tissue at biochemical and morphological levels under exact environmental controls. The studies are involved in examining the changes in chromatin template activity during aging by measuring the number of initiation sites available for RNA polymerase. The quality changes in high mobility group (HMG) non-histone protein associated with the genome during aging will be detected by indirect immunofluorescence technique. The ornithine decarboxylase activity and polyamine concentration which is closely associated with the growth status of the cells will be investigated. Cyclic nucleotide concentration present in the cells may play a regulatory role in cellular function therefore the cyclic nucleotide systems of the aging ovary will be assessed. Cyclic AMP and cyclic GMP level in the growing and aging ovarian cells will be determined by competitive protein binding assay and radioimmunoassay respectively. The adenylyl or quanylyl cyclase can be measured by its ability to catalyze the formation of cyclic nucleotides. The phosphodiesterase activity will be determined by its ability to hydrolyze the cyclic nucleotides. The heterogenous cell populations in the growing and aging ovaries will be obtained by dissociation of the cells with collagenase and then separated by metrizamide density gradient. The proportion of different cell types obtained after gradient separation will be determined by measuring the DNA concentration. In tissue culture, the steroid hormone production and the gonadotropic hormone effect on epithelial-like cells obtained after density gradient separation will continue to be investigated.